By Terence Bradshaw

As many growers know, we are rolling out an expanding orchard scouting program at select sites this year in cooperation with Eric Boire from CPS. This week I got to my sites, both ‘inland’ in Washington and Orange counties, and things were, as expected, behind the main production regions (half-inch green vs tight cluster). Growers in cooler sites still have time to apply oil at 1% by volume, maybe 1.5% if you’re really showing nothing past half-inch green. We are seeing a flare up of San Jose scale in Vermont orchards (just check out some apples from the grocery stores, they’re not hard to find), and a good coating of oil will go a long way toward managing them as well as the mites that we’ll inevitably see come summer.

Insect activity has been relatively low, although the higher temperatures yesterday afternoon may have incited a bit more activity than our traps have caught. Right now we’re looking mainly at tarnished plant bug, and of 40 traps across the state, we’ve only caught one on a TPB trap and another couple in nearby EAS traps- nowhere near treatment threshold. Green fruitworm is a pest that might flare up (and which we have no traps for) and a dose of soft material like Dipel or another Bt product would be good to have on-hand. One nice thing about Bt at this time of year is it’s very safe on bees, but as a lepidopteran (caterpillar)-specific material, it also has no activity against TPB or European apple sawfly, when (if) that one becomes a problem later on.

Apple scab season is here for everyone- keep protected with a protective fungicide going into any rains. Mancozebs, Captan (if no oil has been applied for 7 days before or after), sulfur if organic. Plan on using one of the ‘bigger gun’ materials at pink or petal fall, or immediately after a missed wetting event if that material has good kick-back activity (strobilurins, sterol inhibitors, or SDHIs). There is some evidence of toxicity of sterol inhibitors (Indar, Inspire Super, Procure, Rally, Vintage) to pollinators, to it is best used well before or after bloom when bees (managed and wild) are not visiting flowers.

My main reason for writing today is to get everyone thinking ahead about fire blight. Not panicking, not spraying indiscriminately, but preparing for the event should infection conditions arrive. In that case, you’ll need streptomycin (Harbor, applied at 2 lbs per acre) on-hand since you’ve got 24 hours to apply it after an infection event. Sorry organic growers, strep isn’t approved any more, but Serenade and some other biologicals that I don’t have experience with (Blossom protect, etc.) have some efficacy when applied during an infection event in bloom but not nearly as effective as strep. I expect bloom as early as mid-late next week, so you have time to get some on-hand but if you wait and the big orchards in northeastern New York order up enough material to cover their 2500+ acres (remember they had a FB outbreak last year), it will be in short supply. Any grower who had even a small amount of fire blight last year should have enough on-hand to hit those infected blocks plus susceptible cultivars (Cortland, Paulared, Gala, Honeycrisp) at a minimum, and ideally enough to treat thew whole orchard.

My recommendation to have strep on-hand is different than my recommendation on how to use it, so no one should be spraying strep right now or without consulting a model or hearing otherwise. The fire blight bacteria requires heat prior to and during a potential infection event to multiply and infect, and also requires fresh open wounds (or blossoms) and a few other factors. Until all of those pieces are in place, leave it on the shelf.

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

By Terence Bradshaw

April 25, 2017

Expected showers beginning this afternoon through Wednesday may trigger an apple scab infection period in Vermont orchards. There has been relatively little buds development or and not enough rain in the last week or so to wash off protective residue, so any orchards that received a full-dose protectant fungicide in the past seven days should be protected through this event. However, any rain that does come will add up to sufficiently wash off residue, and warm temperatures Thursday through Saturday should advance bud development substantially. For orchards that are3 at tight cluster now, this may be your last window to apply oil (1% solution, full soaking coverage) before buds advance too far. If you couldn’t get an oil application on and mites are an issue in your orchard, there is a number of different miticides options available now that may be used pre- or post-bloom. Those can be found in the spray tables at netreefruit.org.

Insect pressure is usually pretty low at this time, but we have seen an uptick in tarnished plant bug on buds. If you are trapping with white sticky traps, the threshold before requiring an insecticide application is three or five per trap (wholesale and retail orchards, respectively) at tight cluster and five or eight per trap at pink bud stage. Fruit grown for cideries do not need to be treated for pre-bloom insect pests since their damage is largely cosmetic.

If applying a prebloom insecticide, consider a synthetic pyrethroid material if possible. The jury is still out on the potential for neonicotinoid residue to carry over into pollen and nectar and adversely affect both managed and wild pollinators. And although news was recently made that EPA would not cancel uses of chlorpyrifos (Lorsban and some generics), we would be best to move away from that product as a canopy spray and save it for its use as a trunk spray to manage borers. There is only one use allowed per year, and if a canopy spray is made pre-bloom (the only time allowed for a canopy spray), then its use later on trunks when borers are more active will not be allowed.

Now is a good time to get your first soil-applied nitrogen fertilizer down. In many cases. Split applications are more useful than a single application, timed at tight cluster to pink and a second application at petal fall. Without a foliar analysis (which is always the gold standard for developing fertilizer recommendations), growers should err on applying a total of 30-40 pounds of actual nitrogen per acre whether in one or two applications. This is also a good time to apply the foliar tonic of urea (3#/100 gallons), boron (1# solubor or 0.1-0.2 lb actual B/100 gal) and zinc (many materials, use label rates). I wouldn’t mix this tonic with oil, do one and then the other in this next spray or two if needed.

It’s great weather for planting trees. If you have them in the cooler, get them in the ground.

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

By Terence Bradshaw

It doesn’t take too much fancy software to tell that we are in the middle of a pretty good apple scab infection period in most every orchard in Vermont. Ascospore maturity is estimated at 4-8% for today, and up to 14% in some orchards by the end of the weekend with showers and rain expected for the next four days. Orchards that were covered with copper or another full-rate before April 12 may still have protection, but if more than one inch of rain falls, reapplication during a break in the weather would be warranted. Addition of Vangard or Scala in that spray (in combination with at least a half-rate of EBDC or Captan) will help to manage any infections that slipped though if poor coverage and/or washoff is a concern.

However, in cooler orchards with less tissue showing (and potentially low inoculum from last year), a postinfection material may not be warranted. Use your judgement here and err on covering up if in doubt. This is a good time to put on some oil (2%, good full coverage) but not if using Captan or sulfur in the next or previous 7-10 days.

Organic growers: ignore my suggestion for adding a postinfection fungicide if that means using liquid lime sulfur at this time. The scab risk isn’t great enough to offset the negative impacts that LLS has on orchard ecology and tree health. Save that ‘big gun’ for later in the season. If you feel like you need some retroactive coverage, consider Oxidate or one of the potassium bicarbonate products. Either of those must be applied shortly (<24 hours) within the onset if infection.

I’m away through the weekend, so good luck on this. In between worrying about scab (which, in the big picture, isn’t a massive threat right now), start planting trees and getting other spring activities in order. You can expect to fertilize soon when the soil warms up a bit. And of course everyone is done with pruning and pushing brush, right?

-Terry

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

By Terence Bradshaw

Warm weather over the weekend advanced bud stages, pretty much everything in the Champlain and Connecticut Valleys are at green tip and some orchards are bordering on half-inch green. If you haven’t gotten copper out yet, now is the time, tomorrow (Tuesday 4/18)v looks like a good day wind-wise. We’re also out of any frost risk for the foreseeable future (but not necessarily done for the season so don’t plant out your tomatoes), so you can apply oil any time. At this point I would apply 2% (volume/volume) oil and soak it down real well with 100+, preferably 200 gallons of water per acre. After tight cluster, 1% oil should be used to avoid phytotoxicity.

As temperatures cool down this week, bud development will also slow. However, scab ascospores will continue to mature and by mid-week we can expect 5% or more of ascospores to be available for release during the expected rains and wetting events. This is another reason to cover your trees Tuesday prior to the rain. If you put on a full copper rate Friday or later, you are probably good for now, but if you had spotty coverage or have had substantial bud development, and therefore emergence of new susceptible tissue, since you sprayed, then another preventative fungicide may be called for.

Insect activity is generally pretty quiet now, but tarnished plant bug will start to move as days warm up. This would be a good week to get trapes up for this insect pest. We recommend four white sticky traps per block hung knee high in a visible location, often at the block edges. Traps should be checked at least weekly and treatment for TPB considered if over threshold. Thresholds are variable based on tolerance for cosmetic damage- for apples marketed wholesale, three bugs per trap before tight cluster or five before pink bud would warrant treatment; for retail and pick-your-own orchards, the recommended treatment threshold is five and eight bugs per trap, respectively, for those bud stages. TPOB and other insects managed at pink are usually treated with a synthetic pyrethroid material and that is still the recommendation. In order to conserve wild pollinators, we do not recommend use of neonicotinoid insecticides before petal fall.

1Tarnished plant bug trap (lower left) in tree. Right picture: TPB on trap.

Where trade names or commercial products are used for identification,

no discrimination is intended and no endorsement is implied.

Always read the label before using any pesticide.

The label is the legal document for the product use.

Disregard any information in this message if it is in conflict with the

label.

The UVM Tree Fruit and Viticulture Program is supported by the

University of Vermont Agriculture Experiment Station, a USDA NIFA E-IPM

Grant, and USDA Risk Management Agency Funds.

By Terence Bradshaw

April 5, 2017

NEWA Apple Scab and Phenology Models

We don’t need computers and models to tell us that by mid-April we ought to expect apple bud break to be around the corner, and with temperatures in the 70s forecast for Monday and Tuesday of next week, I expect many orchards to be at green tip by then. Of course this does have us looking to apple scab development models to get a sense of where we’ll be on that front next week, and more than one grower noticed in the past day or two that there is an anomaly in the NEWA apple scab model for many sites. There are two models on the scab page, one which is predicting your bud stage, and the other which predicts apple scab ascospore maturity. The latter model relies on McIntosh green tip as the biofix to start accumulating degree days, so if the model guesses wrong, then your accumulation may be incorrect.

However, remember that these are simplified models that are predicting complex biological phenomena. The development of apple tree phenology is dependent on more than just air temperature, and of course there are multiple methods of measuring degree days to further complicate things. So the model that guesses the green tip and other phenology stages for your site may not be correct, and you should always enter site-specific data for your orchard to increase the accuracy of the model. On the other hand, the predictive phenology model built into the apple scab model is a bit more conservative than the previously mentioned and more visible phenology model that populates the ‘green tip date’ box on the site. During a conference call yesterday with NEWA state coordinators and overall program coordinator Dan Olmstead and former coordinator/NEWA developer Julie Carroll, we learned that they intentionally set the ‘green tip predictor’ in the scab model a bit more conservative so as to not miss early ascospore development. The result is that the apple scab model can show accumulated degree days since green tip while the green tip predictor model says you are still xx days away from green tip.

The moral of the story is twofold. First, for any NEWA model that calls for a biofix you will get more accurate results if you enter an actual value for your orchard. Second, remember that these are models and therefore are well-educated guesses, and thus you should not assume 100% confirmation to actual biology in the orchard. They are good, and have become invaluable to all of our work, but sometimes common orchard sense (e.g., there’s no green tissue so there’s no scab risk to worry about) is still important.

What About the First Scab Sprays?

I’ll go out on a limb and say that in the major apple production areas we will have green tip next week. However, the long-term weather looks relatively mild, warm but not outrageous, so I expect bud phenology and ascospore development to move along at a moderate pace. If your orchard was clean last year, and I mean you know it was clean by assessing lesions in the fall using a PAD method, then you can likely skip the first scab spray, depending on when that is needed. Of course we need rain and extended leaf wetness to initiate an infection, so if it’s dry, you don’t need protection. After the next couple of days where the prognosticator in me says with 100% certainty that it will be rainy (but without green tissue on trees to be infected), I don’t know what the rain situation will be like next week.

However, we will be advancing from green tip toward 1/2” green, and that is the last window to apply copper which will be extremely important to do on any orchard that had fire blight last year. That copper spray will also give you 5-7 days’ protection against scab, so consider that your first spray against both of those diseases. Copper’s effect on fire blight is to reduce overwintering inoculum on wood, this assumes that you were thorough in pruning out infected wood, especially those big cankers that can form on limbs and trunks. After 1/2” green tip, you run the risk of causing fruit russet with copper application which can severely downgrade fruit marketability. If you are growing fruit for sale to cideries and know for certain that you will not be marketing for fresh fruit, you may be able to extend your copper spray window a bit, or consider using low rates of copper later in the growing season for management of apple scab or fire blight. However, there are generally better alternative products to use later in the season if you plan ahead, unless you are limited to organically-acceptable materials.

I would plan on applying copper to any orchard that had any amount of fire blight last year and which is showing green tissue or at least solid silver tip as soon as you have a suitable spray window. If possible, I would plan on applying copper to any orchard, period, that is between silver tip and half-inch green in the next 7-10 days. There is a pile of materials out there and for all intents and purposes for this delayed dormant spray any of them are effective as long as you are applying a good full rate of copper ions. The standard dry materials like Champ, C-O-C-S, Cuprofix, Kocide, etc. will give you the best bang for the buck here, and I would apply the full label rate for any of them and thoroughly spray the whole orchard. The only caveat I offer is if phenology advances rapidly before you can get out there and the trees are at 1/2” green tip, in that case, I would apply a low to middle rate. After 1/2” green tip, unless you don’t care about fruit finish, I would avoid copper.

Cleaning Up

The next week looks good for performing orchard sanitation to get things ready for spring- wrap up your pruning, push any brush out of the rows, flail mow leaves and fine brush, and consider applying a coarse urea spray (44 lb in 100 gal water applied per acre, directed at the leaf litter). The latter two practices can reduce overwintering scab inoculum and allow you, if you had low incidence of scab last year and were thorough in flail mowing or applying the urea, to skip a scab spray, maybe two, while ascospore development is low.

Looking Ahead

Whenever I want to show someone scale on fruit I am pretty sure I can easily find fruit with damage at any supermarket, and many of those fruit are from Vermont orchards. In recent years many orchards have been backing off from oil applications which really do a good job reducing overwintering scale, mites, and, to a lesser extent, some other insects such as codling moth and aphids. Oil application must be made at a dilute setting, generally 100 gallons of water or more per acre, so they take a while. They are most effective against mites just prior to them hatching, and therefore are best applied around tight cluster, so we’ll discuss again in a week or two. You can also use lower rates at that time, so the cost is a little better. But if your orchard is clean and you’re looking for things to do this coming week, feel free to apply a 2% oil in all blocks. Oil can be mixed with copper, but it should not be applied 48 hours before or after freezing weather, which is another reason why growers tend to opt for later applications.

Don’t Forget- The New England Tree Fruit Management Guide is now housed at: http://netreefruit.org.